This invention relates to an apparatus for rearranging sheets of paper or like material into stacks. Typically, the apparatus is incorporated with a printing press for delivery of printed sheets of paper in successive stacks on a delivery conveyor.
A typical prior art apparatus in the field is disclosed in Japanese Unexamined Patent Publication No. 62-121176. It includes what is known to the specialists as a delivery fan, a rotor having axial rows of convolute blades mounted thereon at constant circumferential spacings. Issuing from a frictional belt conveyor system one by one, printed sheets of paper are successively received one in each spacing between the blades of the delivery fan in rotation. The sheets revolve with the delivery fan until, approximately half a revolution later, they comes into successive abutment against a set of stop blades which are arranged interdigitatingly with the fan blades. Thereupon, with the continued rotation of the delivery fan, the sheets will be pushed out of the fan blade spacings and, thus falling off the delivery fan, deposited upon an underlying tray to be stacked thereon.
Another important component of the delivery apparatus is a temporary sheet holder which is angularly displaceable radially outwardly of the delivery fan about the same axis therewith. When the sheets are stacked to a predefined height on the tray, the sheet holder will be turned to its working position between the delivery fan and the tray for temporarily receiving the sheets that are subsequently released from the fan. The sheet holder will be retracted away from under the delivery fan after the preformed stack on the tray has been carried away and a new tray positioned in its stead. The sheets that have been deposited on the sheet holder will fall off the same onto the new tray during the retraction of the sheet holder, and the sheets subsequent released from the delivery fan will fall onto the new tray and form another stack thereon.
An objection to this prior art apparatus is that the delivery fan and the temporary sheet holder are driven by different means comprising separate electric stepper motors. Difficulties have been experienced as a consequence in realizing strict synchronism in turning the sheet holder to its working position with the rotation of the delivery fan. In event the delivery fan and the sheet holder are driven out of synchronism, mutual interference has been easy to occur between the sheet holder and the sheets falling off the delivery fan. The frequent results have been the creasing or wrinkling of the sheets and the uneven or irregular stacking thereof.
Another objection concerns the way the sheets temporarily deposited on the sheet holder are subsequently dropped therefrom onto the new tray when the sheet holder is angularly retracted about the delivery fan axis. The lowermost one of the sheets on the sheet holder has tended to stick to it so fast that the lowermost sheet has often failed to come off the sheet holder being retracted, again resulting in disorderly or uneven stacking of the sheets.
The present invention has it as an object to realize exact synchronism in angular displacement of the temporary sheet holder to its working position with the rotation of the delivery fan.
Another object of the invention is to ensure that all the sheets that have fallen upon the temporary sheet holder smoothly come off the same upon its retraction.
Still another object of the invention is to avoid any interference between the sheets falling off the delivery fan and the sheet holder traveling to its working position.
Briefly, the present invention may be summarized as an apparatus for delivery of sheets of paper or like material in successive stacks, comprising a delivery fan for receiving successive sheets from some infeed means while in rotation in a prescribed direction. The delivery fan is provided with abutment means to be hit by the sheets being carried thereby, the sheets on hitting the abutment means falling off the delivery fan with continued rotation thereof, onto underlying delivery means to be stacked thereon. A temporary sheet holder is angularly displaceable about the same axis as the delivery fan between a working position, where the temporary sheet holder temporarily receives the sheets falling off the delivery fan pending replacement of a preformed stack of sheets on the delivery means, and a retracted position, spaced upstream from the working position with respect to the rotational direction of the delivery fan, where the temporary sheet holder allows the sheets to fall from the delivery fan onto the delivery means.
Characteristically, the temporary sheet holder is mounted to the shaft of the delivery fan via overrunning clutch means which prevent the temporary sheet holder from running faster than the delivery fan shaft from the retracted toward the working position, and which allow the temporary sheet holder to rotate independently of the delivery fan shaft from the working toward the retracted position. Resilient means act between the temporary sheet holder and a stationary part of the apparatus for biasing the former from the retracted toward the working position and hence for causing, in cooperation with the overrunning clutch means, the temporary sheet holder to travel at the same angular velocity as the delivery fan from the retracted to the working position. Drive means are provided for moving the temporary sheet holder from the working to the retracted position against the bias of the resilient means.
When the sheets falling from the delivery fan are being stacked on the delivery means, the temporary sheet holder is positively retained in the retracted position by the drive means. Then, unlocked from the retracted position upon stacking of a prescribed number of sheets on the delivery means, the temporary sheet holder tends to run faster than the delivery fan to the working position under the influence of the resilient means. Actually, however, the sheet holder is constrained by the overrunning clutch means to joint travel with the delivery fan at the same angular velocity therewith.
Exact synchronism is thus attained between delivery fan and temporary sheet holder. So driven to its working position, the sheet holder will seldom interfere with the sheets falling from the delivery fan, nor will an error easily occur in the number of sheets forming each stack.
Another feature of the invention concerns the construction of the temporary sheet holder itself. The sheet holder includes a set of sheet holder prongs spaced axially of the delivery fan and each extending circumferentially of the delivery fan. Each sheet holder prong is made hollow, defining a plenum chamber therein, and has a suitable number of air exit openings formed least in its surface facing the delivery fan and, preferably, in part of its other surface facing away from the delivery fan.
Air under pressure flows out all the openings in the sheet holder prongs at least when the sheet holder is traveling toward its working position. As the sheet holder enters between any two consecutive sheets falling from the delivery fan, the outflowing air will widen the space therebetween, making it all the more unlikely for the sheet holder to touch, much less wrinkle or otherwise damage, the sheets.
Air is also to be emitted from the sheet holder prong surfaces when the sheet holder is retracted from its working position. The sheets that have been deposited on the sheet holder during replacement of the preformed sheet stack are to fall by gravity from the sheet holder upon its retraction, in order to form another stack on the delivery means. There is no risk of the sheets remaining stuck to the sheet holder prong surfaces, and so being carried away to the retracted position of the sheet holder, as air issues from the perforated prong surfaces.
The above and other objects, features and advantages of the invention and the manner of realizing them will become more apparent, and the invention itself will best be understood, from the following description taken together with the attached drawings showing the preferred embodiment of the invention.